1. Field of the Invention
The present invention relates to a magnetic recording medium, and in particular to a removable flexible magnetic recording medium provided with signals for servo tracking.
The present invention also relates to a drive apparatus for driving a magnetic recording medium.
2. Description of the Related Art
Generally speaking, with regard to magnetic storage mediums, there is a demand for increased storage capacity and low cost. Further desired are so-called high-speed access mediums, which are capable of advantageously reading out the data of a desired location in a short time. Examples of these high-density magnetic recording mediums include the magnetic recording mediums such as the conventional hard disks or flexible disks used in ZIP (Iomega) drives or the like. In comparison to floppy disks, the data recording region of a high-density recording medium such as that described above is provided with a narrower track. So-called tracking servo technology, wherein the magnetic head accurately scans the narrow width track, plays a substantial role in achieving a high S/N ratio. A conventional sector servo method is widely used for performing the tracking servo operation.
The sector servo method is a method wherein servo data such as the track positioning servo data, track address data signals, clock signals, and the like are recorded within servo fields distributed regularly at uniform angles over the data recording surface of the disk. A magnetic head scans these servo fields and reads out the servo data to confirm and correct its position. In general, a portion of the servo signal is recorded at a distance displaced by ½ the width of the track from the center line of said track, and the remaining components of the servo signal (i.e., the address data signals, clock signals and the like) are recorded on the center line of the track at an entire track pitch width. The data track width is narrower than the recording width of the servo signal, which encompasses the entire track width, and a guard band is formed on both sides of the data track.
The servo data must be “preformatted”, that is, recorded on the magnetic recording medium in advance at the time of the manufacture thereof. Presently, servo recording apparatuses record servo signals on disks one track at a time, at a ½ track pitch. Therefore, a significant amount of time is required for the preformatting operation of one disk; whereby a problem exists from the standpoint of manufacturing efficiency.
On the other hand, magnetic transfer methods realizing accurate and efficient preformatting, wherein the data such as a servo signal or the like borne on a master medium is magnetically transferred therefrom to a magnetic recording medium, have been proposed in, for example, Japanese Unexamined Patent Publication Nos. 63(1988)-183623, 10(1998)-40544, and 10(1998)-269566.
According to these magnetic transfer technologies, a master medium having an uneven pattern provided with a magnetic layer on the surfaces of the protrusion portions thereof corresponding to the data that is to be transferred to a magnetic recording medium (a slave medium) is prepared. By bringing this master medium into close contact with a slave medium to form a conjoined body and applying a transfer magnetic field thereto, a magnetic pattern corresponding to the data (e.g., a servo signal) borne on the master medium is transferred to the slave medium. The preformatting can be performed without changing the relative positions of the master medium and the slave medium, that is, while the two media remain relatively static. Therefore not only is it possible to perform an accurate recording of the preformat data, it becomes possible to advantageously do so in an extremely short time.
At present, further increases in the data storage capacity of flexible disks magnetic recording mediums are sought. To this end, efforts to narrow the track width to less than 3 μm, or even less than 1 μm have been undertaken. In order to achieve such narrow track widths, improved magnetic recording mediums have been developed, and MR heads, PRML channels and the like have been employed to satisfy the record/playback properties of a magnetic recording medium having a narrow track width such as that described above. However, even with an elaborately well designed and stable HMI (head-medium interface), a flexible disk cannot avoid vertical media run-out on the order of 1-10 μm. With regard to the sector servo method, the position of the head is corrected within the servo fields, and the data regions between the servo fields are position control free regions. By further narrowing the track width, the size of the position control free region becomes relatively larger with respect to the servo field. Therefore, in a sector servo method having the conventional number of servo fields, it is difficult to achieve adequate tracking control (track following). Although it is possible to achieve an improvement in tracking control accuracy by increasing the number of servo fields, because data regions and servo fields are provided within the data track according to the sector servo method, a problem arises in that if the number of servo fields is increased, the data region is reduced.